imported vehicle

A lot of imports to the UK were personal imports from Belgium, etc. back in the very early noughties when car prices were considerably higher in the UK than the pre-tax price in some European countries.  The main thing to watch for are trim and option level difference, e.g. there may not have been an official SE spec in some countries so you should check that all of the kit associated with a UK spec SE is present.  Sometimes people ordering overlooked some of the less visible options (e.g. auto dimming rear view mirror).

If its more recent than that then it could a factory collection.  I'm not sure if there is still an advantage for British Forces posted overseas but that also used to give rise to a good few imports in the UK too.

As long as the paperwork is in order and the spec looks like it matches a UK car then I wouldn't be put off.  The UK trade seem to mark them down on price over a UK car so make sure you don't overpay for it.